/*
 * Copyright 2002-2012 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.jdbc.core.metadata;

import org.springframework.dao.InvalidDataAccessApiUsageException;
import org.springframework.jdbc.support.nativejdbc.NativeJdbcExtractor;
import org.springframework.util.ReflectionUtils;

import java.lang.reflect.Method;
import java.sql.*;

/**
 * Oracle-specific implementation of the {@link org.springframework.jdbc.core.metadata.TableMetaDataProvider}.
 * Supports a feature for including synonyms in the metadata lookup. Also supports lookup of current schema using
 * the sys_context.
 *
 * <p>Thanks to Mike Youngstrom and Bruce Campbell for submitting the original suggestion for the Oracle
 * current schema lookup implementation.
 *
 * @author Thomas Risberg
 * @author Juergen Hoeller
 * @since 3.0
 */
public class OracleTableMetaDataProvider extends GenericTableMetaDataProvider {

    private final boolean includeSynonyms;

    private String defaultSchema;


    public OracleTableMetaDataProvider(DatabaseMetaData databaseMetaData) throws SQLException {
        this(databaseMetaData, false);
    }

    public OracleTableMetaDataProvider(DatabaseMetaData databaseMetaData, boolean includeSynonyms) throws SQLException {
        super(databaseMetaData);
        this.includeSynonyms = includeSynonyms;
        lookupDefaultSchema(databaseMetaData);
    }

    @Override
    protected String getDefaultSchema() {
        if (defaultSchema != null) {
            return defaultSchema;
        }
        return super.getDefaultSchema();
    }

    @Override
    public void initializeWithTableColumnMetaData(DatabaseMetaData databaseMetaData,
                                                  String catalogName, String schemaName, String tableName) throws SQLException {

        if (!this.includeSynonyms) {
            logger.debug("Defaulting to no synonyms in table metadata lookup");
            super.initializeWithTableColumnMetaData(databaseMetaData, catalogName, schemaName, tableName);
            return;
        }

        Connection con = databaseMetaData.getConnection();
        NativeJdbcExtractor nativeJdbcExtractor = getNativeJdbcExtractor();
        if (nativeJdbcExtractor != null) {
            con = nativeJdbcExtractor.getNativeConnection(con);
        }
        boolean isOracleCon;
        try {
            Class<?> oracleConClass = getClass().getClassLoader().loadClass("oracle.jdbc.OracleConnection");
            isOracleCon = oracleConClass.isInstance(con);
        } catch (ClassNotFoundException ex) {
            if (logger.isInfoEnabled()) {
                logger.info("Couldn't find Oracle JDBC API: " + ex);
            }
            isOracleCon = false;
        }

        if (!isOracleCon) {
            logger.warn("Unable to include synonyms in table metadata lookup. Connection used for " +
                    "DatabaseMetaData is not recognized as an Oracle connection: " + con);
            super.initializeWithTableColumnMetaData(databaseMetaData, catalogName, schemaName, tableName);
            return;
        }

        logger.debug("Including synonyms in table metadata lookup");
        Method setIncludeSynonyms;
        Boolean originalValueForIncludeSynonyms;

        try {
            Method getIncludeSynonyms = con.getClass().getMethod("getIncludeSynonyms", (Class[]) null);
            ReflectionUtils.makeAccessible(getIncludeSynonyms);
            originalValueForIncludeSynonyms = (Boolean) getIncludeSynonyms.invoke(con);

            setIncludeSynonyms = con.getClass().getMethod("setIncludeSynonyms", new Class[]{boolean.class});
            ReflectionUtils.makeAccessible(setIncludeSynonyms);
            setIncludeSynonyms.invoke(con, Boolean.TRUE);
        } catch (Exception ex) {
            throw new InvalidDataAccessApiUsageException("Couldn't prepare Oracle Connection", ex);
        }

        super.initializeWithTableColumnMetaData(databaseMetaData, catalogName, schemaName, tableName);

        try {
            setIncludeSynonyms.invoke(con, originalValueForIncludeSynonyms);
        } catch (Exception ex) {
            throw new InvalidDataAccessApiUsageException("Couldn't reset Oracle Connection", ex);
        }
    }

    /*
     * Oracle implementation for detecting current schema
     *
     * @param databaseMetaData
     */
    private void lookupDefaultSchema(DatabaseMetaData databaseMetaData) {
        try {
            CallableStatement cstmt = null;
            try {
                cstmt = databaseMetaData.getConnection().prepareCall("{? = call sys_context('USERENV', 'CURRENT_SCHEMA')}");
                cstmt.registerOutParameter(1, Types.VARCHAR);
                cstmt.execute();
                this.defaultSchema = cstmt.getString(1);
            } finally {
                if (cstmt != null) {
                    cstmt.close();
                }
            }
        } catch (Exception ignore) {
        }
    }

}
